Phenol-formaldehyde resin binders are routinely used for commercial applications involving siliceous materials because of their low cost and availability. These resins are sold as aqueous solutions that contain free formaldehyde. Moreover, phenolic resins may emit formaldehyde upon heat curing and storage.
Fibers, particularly glass fibers, benefit from treatment with binders. The self-abrasion of glass fibers is known to cause surface defects which reduce their mechanical properties. Conventional treatment is to spray resin binder formulations onto glass fibers immediately after fiberization or attenuation. The resin binder protects the fiber and gives dimensional stability to structures formed from a multiplicity of fibers by fixing or immobilizing junction points between fibers.
An important use of glass fiber is in the manufacture of fiberglass insulation, either in the form of mats or fiber agglomerates. Coated fiberglass is conventionally fabricated into fiberglass insulation in high speed processes. These highly automated fiberglass forming processes require a binder having a combination of important properties.
Commercial prior art binders are based upon various resins such as phenol-formaldehyde resins and melamine formaldehyde resins. Such resins are typically provided in aqueous solutions containing free formaldehyde. These phenol-formaldehyde resins are water soluble, must be refrigerated before use, and are oven cured at about 177.degree. C. to about 288.degree. C.
A shortcoming of the prior art binder resins is that they tend to emit formaldehyde during application and storage. In particular, formaldehyde is emitted during the manufacture of fiberglass insulation. Additionally, the decomposition tendencies of the prior art phenolic resins are aggravated when stored under conditions of heat and humidity.
It is desirable to develop fiberglass binders which have reduced formaldehyde emission levels and are suitable for the treatment of siliceous substrates such as fiberglass.